you have been studying the effects of loss-of-function mutations in the cdk inhibitor protein p21. you add the drug fucoxanthin to 2 cell cultures, one containing wild-type p21 and one containing non-functional mutant p21. fucoxanthin is known to induce cell-cycle arrest in g1. after a day, you supplement the cells with a deoxythymidine analog (brdu), collect the cells after an hour, treat them with anti-brdu antibody and the fluorescent dna stain dapi, and finally subject them to fluorescence-activated cell sorting (facs). the anti-brdu signal indicates dna synthesized during the time (1 hour; a cell cycle takes ~24 hours) of brdu addition. the dapi signal indicates the amount of dna in a cell. indicate which boxed region (1, 2, or 3) in the facs plots corresponds better to each of the following phases of the cell cycle.